class Solution {
public:
    int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid)
    {
        if (obstacleGrid[0][0] == 1) return 0;
        int n = obstacleGrid.size(), m = obstacleGrid[0].size();
        vector<vector<int>> dp(n, vector<int>(m, 0));
        dp[0][0] = 1;
        bool flag = false;
        for (int i = 1; i < n; i++)
        {
            if (obstacleGrid[i][0] == 1) flag = true;
            if (!flag) dp[i][0] = 1;
            else dp[i][0] = 0;
        }
        flag = false;
        for (int i = 1; i < m; i++)
        {
            if (obstacleGrid[0][i] == 1) flag = true;
            if (!flag) dp[0][i] = 1;
            else dp[0][i] = 0;
        }
        for (int i = 1; i < n; i++)
        {
            for (int j = 1; j < m; j++)
            {
                if (obstacleGrid[i][j] == 1)
                {
                    dp[i][j] = 0;
                    continue;
                }
                dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
            }
        }
        return dp[n - 1][m - 1];
    }
};